The present invention relates to an alarm system for fire, gas leakage or the like wherein sensors are installed in several locations to generate analog output signals respectively corresponding to smoke concentrations, gas concentrations, or temperatures at these locations, the sensors being accessed by addresses from a receiver installed in a remote location so that the accessed sensors supply analog signals to the receiver. More particularly, the present invention relates to a sensor test circuit for testing operation of the sensors from a remote location.
In a conventional alarm system of this type, a smoke test for checking sensors located at the corresponding terminals has been conducted such that smoke is deliberately generated to simulate an emergency at each sensor position and a sensor output is then received at a receiver. Therefore, maintenance personnel at each sensor location must communicate with those at the receiver location. However, it is very difficult to set a smoke concentration at a desired value. Furthermore, time-consuming, cumbersome testing procedures are required, resulting in inconvenience.